Field of the Invention
The present invention generally relates to a fixing device used in an image forming apparatus such as a copier, a printer, a facsimile machine, or a multifunction machine including at least two of these functions, and an image forming apparatus including the fixing device.
Discussion of the Background
In general, electrophotographic image forming apparatuses, such as copiers, printers, facsimile machines, and multifunction machines including at least two of these functions, include an image carrier on which an electrostatic latent image is formed, a developing unit to develop the latent image with toner, a transfer member, and a fixing device. The developed image (toner image) is transferred from the image carrier onto a sheet of recording media by the transfer member and then fixed on the sheet with heat and pressure by the fixing device.
Fixing devices may include an endless belt, a pressure roller that contacts an outer circumferential surface of the belt and pressures the belt, a stationary member fixed inside the belt to press against the rotary member via the belt, and a heater for heating the belt. The endless belt and the pressure roller contact each other, and a nip area is formed in the contact area.
When the fixing device heats and pressurizes the toner image on a recording medium by the nip area, the toner image is fixed on a recording medium.
Market demand for high-speed image forming apparatuses makes it desirable that a toner image be fixed on a recording medium properly in the fixing device even when the image forming apparatus forms the toner image on the recording medium at high speed with a shortened warm-up time period.